Catalyst for propylene polymerization

ABSTRACT

A catalyst for use in the formation of polypropylene is disclosed that comprises a titanium compound having at least one titanium-halogen bond, supported on an activated, amorphous magnesium dihalide support that is essentially free of alkoxy functionality, with a titanium metal content of no more than about 2 wt %, based on the weight of the support, and an internal donor component. This catalyst is made by a: forming a combination of titanium tetrachloride, magnesium-containing compound that can be converted to magnesium dihalide and internal electron donor in an aromatic hydrocarbon solvent and bringing that combination to elevated temperature to form an intermediate product; washing the intermediate product with an aromatic hydrocarbon solvent at elevated temperature to produce a washed product and a supernatant followed by decantation of the supernatant therefrom; treating the washed product with titanium tetrachloride in an aromatic hydrocarbon solvent to form a treated product and a supernatant followed by heating of the treated product and supernatant, decantation of the supernatant therefrom, and washing of the treated product with an aromatic hydrocarbon solvent at elevated temperature; decantation of the supernatant therefrom, and washing of the treated product with an aromatic hydrocarbon solvent preferably at least one or two more times; and addition of an aliphatic hydrocarbon solvent to the treated product with decantation of the solvent therefrom to form a washed product which can be used as a propylene polymerization catalyst. If desired, after the formation of the washed product resulting from addition of the aliphatic hydrocarbon solvent, mineral oil can be added to the washed product to form a slurry containing the final catalyst.

BACKGROUND OF THE INVENTION

[0001] This invention relates to the synthesis of a catalyst for thepolymerization of propylene. This catalyst has high activity, andproduces a polymer product having high stereospecificity and high bulkdensity. The catalyst's activity is long lived and it shows a goodtemperature response. All of these features are desirable for acommercial propylene polymerization catalyst.

SUMMARY OF THE INVENTION

[0002] The present invention relates to a process for forming apropylene polymerization catalyst. This process, in general terms,comprises: forming a combination of titanium tetrachloride, a soluble orinsoluble magnesium-containing compound that can be converted tomagnesium dihalide, such as a magnesium chloroalkoxide, and an internalelectron donor, such as phthalate ester, in an aromatic hydrocarbonsolvent and bringing that combination to elevated temperature to form anintermediate product which is separated by, for example decantation;washing the intermediate product with an aromatic hydrocarbon solvent atelevated temperature to produce a washed product and a supernatantfollowed by decantation of the supernatant therefrom; treating thewashed product with titanium tetrachloride in an aromatic hydrocarbonsolvent, preferably two or three more times, to form a treated productand a supernatant followed by heating of the treated product andsupernatant, decantation of the supernatant therefrom, and washing ofthe treated product with an aromatic hydrocarbon solvent at elevatedtemperature, as previously described, with separation of the desiredproduct (for example, also by decantation); and addition of an aliphatichydrocarbon solvent to the treated product with decantation of thesolvent therefrom to form a washed product which can be used as apropylene polymerization catalyst, optionally after the addition ofmineral oil to the washed product to form a slurry containing thecatalyst.

[0003] The soluble or insoluble magnesium-containing compound that canbe converted to magnesium dihalide can be selected from one or more ofthe following types of compound: magnesium dialkoxides (e.g., magnesiumdiethoxide); chloromagnesium alkoxides (e.g., chloromagnesium ethoxide);magnesium dihalide electron donor adducts (e.g., MgCl₂(EtOH)_(x) andMgCl₂(THF)_(x), where THF is tetrahydrofuran and x in both cases is≧0.5; alkylmagnesium halides (“Grignards”, such as chlorobutylmagnesium;and dialkylymmagnesium compounds, such as butylethylmagnesium. In allthe foregoing classes of compound, the number of carbon atoms in thealkoxide/alkyl moiety or moieties, as appropriate, will range from oneto about twelve, preferably four. Any of such precursors can besupported on an inert carrier, such as silica.

[0004] The internal electron donor can be selected from the known typesof internal donor including the following classes: the phthalates andtheir derivatives; the benzoates and their derivatives; the silanes andsiloxanes; and the polysilanes and polysiloxanes.

[0005] In accordance with the present invention, the selected magnesiumdichloride source compound cannot be a magnesium dialkoxide when theselected internal donor is a halo phthaloyl derivative.

[0006] The process of this invention produces a polymerization catalystthat comprises a titanium compound having at least one titanium-halogenbond that is supported on an activated, amorphous magnesium dihalidesupport that is essentially free of alkoxy functionality, the titaniummetal content in the catalyst preferably being no more than about 2 wt%, based on the weight of the support, and an internal donor, such as aphthalate ester donor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] While the following description focuses upon a certain preferredmagnesium dihalide source material, namely, chloromagnesium ethoxide andinternal donor (diisobutyl phthalate), it is to be understood that thebroader possibilities for the selection of each, just describedhereinabove, can be utilized in place of these two selections.

[0008] The catalyst of the present invention is made using a series ofmultiple treatment cycles, each of which involves the reaction ofmixtures of titanium tetrachloride and an alkylbenzene solvent, such astoluene, with a support precursor followed by treatment of the solidwith an aromatic hydrocarbon solvent, which is preferably analkylbenzene solvent. Representative aromatic solvents that can be usedin the process that is described herein include benzene, suchhaloaromatic solvents as the chlorobenzenes, and such alkylbenzenesolvents as toluene and xylene. These reaction steps are carried out atelevated temperature. If a lower boiling solvent of this type, such asbenzene, is used it may be necessary to use superatmospheric pressure toget to the desired temperature conditions. During the first titaniumtetrachloride/aromatic solvent reaction step, an internal phthalateester donor, such as the preferred diisobutylphthalate, is added. If theultimate polymer product that is to be produced is to have desirableparticle size and morphology characteristics, an appropriate particlesize and morphology-controlled support precursor needs to be used. Thetreatment cycles then need to be carried out in such a manner as topreserve these features in the final catalyst so that the polymerproduct replicates those features.

[0009] The initial step of the process of the present invention involvesforming a combination of titanium tetrachloride, magnesiumchloroalkoxide, for example, and phthalate ester in an aromatic solventand bringing that combination to elevated temperature to form anintermediate product. The preferred magnesium chloroalkoxide willcontain from one to about twelve carbon atoms in the alkyl moietytherein. The most preferred magnesium chloroalkoxide is magnesiumchloroethoxide. Toluene has been found to be a preferred alkylbenzenesolvent for use, with xylene, ethylbenzene, propylbenzene,isopropylbenzene, and trimethylbenzene also being useful. The preferredphthalate ester may contain from one to about twelve carbon atoms in thealkyl groups therein, with representative compounds including dimethylphthalate, diethyl phthalate, di-n-propyl phthalate, di-isopropylphthalate, di-n-butyl phthalate, di-butyl phthalate, di-tert-butylphthalate, diisoamyl phthalate, di-tert-amyl phthalate, di-neopentylphthalate, di-2-ethylhexyl phthalate, and di-2-ethyldecyl phthalate. Thedonor can be added at room temperature to the other components and themixture can then be brought to elevated temperature (for example, atabout 100° C. to about 140° C., preferably from about 110° C. to about120° C.) or it can be added to the other two components either at roomtemperature and heated up to about 100° C. or can be added to thosecomponents after they have been heated to a desired temperature. Theamount of titanium tetrachloride to aromatic solvent will generallyrange from about 40% to 80% on a volume basis and, generally, from aboutthree to about four treatment steps have been found to be adequate. Thevolume of titanium tetrachloride and solvent to grams of supportprecursor that is employed will generally be from about 5 to about 10milliliters of titanium tetrachloride and solvent per gram of supportprecursor. The combination of components is preferably held together forup to about ten hours, preferably from about one to about two hours andis agitated. The intermediate solid product from this initial reactionstep is then recovered after the supernatant is decanted.

[0010] The intermediate product from the initial step is then washedwith an aromatic hydrocarbon solvent, such as an alkylbenzene solvent(for example, toluene), at elevated temperature (e.g., from about 100°C. up to the boiling point of the solvent) to produce a washed productand a supernatant phase. The washing can be practiced in up to aboutthree separate washing steps. The supernatant in each washing step isdecanted from the washed product. This washing serves to removeundesirable by-products that contain titanium. The volume of aromaticsolvent that is used per gram of support precursor in this step willgenerally range from about 5 to about 25 milliliters per gram.

[0011] The washed product from the preceding step is then treated withtitanium tetrachloride in an aromatic solvent of the type previouslydescribed under the previously described conditions to form a treatedproduct and a supernatant. This step converts unreacted alkoxidemoieties of the starting magnesium chloroalkoxide reagent and extractsundesired titanium-containing by-products. This combination is thenheated (e.g., at from about 100° C. to about 140° C.) followed bydecantation of the supernatant phase that exist and washing of thetreated product with an aromatic hydrocarbon solvent, preferably in awashing cycle of from one to two step(s) each.

[0012] After the desired number of treatment/wash cycles, the productfrom the preceding step then has an aliphatic hydrocarbon solvent, suchas hexane, added to it with decantation of the resulting supernatantphase therefrom. Washing of the catalyst with aliphatic solvent (e.g.,up to about 3-8 separate washing steps) serves to remove free titaniumtetrachloride and residual aromatic solvent. This forms a washed productthat can be used as the catalyst.

[0013] An optional final step is the addition of mineral oil to thewashed product from the preceding step to form a mineral oil/catalystslurry that can be employed as the propylene polymerization catalyst.Drying of this slurry is usually avoided since it can result in asubstantial decrease in catalyst activity (e.g., up to as much as 50%).

[0014] The catalyst composition that can be formed from the previouslydescribed process appears to be a novel composition of matter in certainembodiments. It comprises a titanium compound having at least onetitanium-halogen bond that is supported on an activated, amorphousmagnesium dihalide support that is essentially free of alkoxyfunctionality. In its broadest embodiment, the catalyst composition hasthe following physical parameters: weight percent titanium—from about 1%to about 4%; weight percent phthalate ester—from about 10% to about 25%;phthalate ester to titanium molar ratio—from about 0.9 to about 2;weight percent magnesium—from about 14% to about 23%; magnesium totitanium molar ratio—from about 7 to about 30; surface area—from about250 m²/gm to about 500 m²/gm; pore volume—from about 0.2 cc/gm to about0.5 cc/gm; and average pore diameter—no more than about 50 Angstroms.

[0015] More preferred embodiments of the catalyst composition have thefollowing physical parameters: weight percent titanium—less than about2.0%, most preferably from about 1% to about 2.5%; weight percentphthalate ester—from about 10% to about 20%; phthalate ester to titaniummolar ratio—from about 1 to about 1.9; weight percent magnesium—fromabout 18% to about 21%; magnesium to titanium molar ratio—from about 14to about 29; surface area—from about 300 m²/gm to about 500 m²/gm; porevolume—from about 0.2 cc/gm to about 0.4 cc/gm; and average porediameter—no more than about 35 Angstroms.

[0016] Based on the very high productivity and low titanium (Ti) contentof the catalyst of this invention, the polypropylene product that isformed from using that catalyst composition is deemed to be a novelcomposition having a very low residual Ti concentration. Depending uponthe polymerization time and temperature, polymer with less than about0.20 ppm Ti, preferably less than 0.15 ppm Ti, most preferably less than0.10 ppm Ti can be produced.

[0017] The Examples that follow are provided to illustrate certainpreferred embodiments of the invention.

EXAMPLE 1

[0018] Catalyst Preparation

[0019] In a nitrogen filled dry box, 10.0 g of a mixed phase ClMg(OEt)was charged into a 500 ml 4-neck round bottom flask. The flask wasfitted with a mechanical stirrer, nitrogen inlet adapter, condenser withnitrogen outlet adapter, and septum, and removed from the dry box to aSchlenk line. Then, 30 ml of dry toluene was added, the mixture wasstirred to suspend the solid, and 20 ml of TiCl₄ was added to thestirred slurry at a rate that maintained the temperature ≦25° C. Theslurry was heated to 70° C. and 3.78 g of diisobutylphthalate was added.The mixture was heated to 115° C. and was held at this temperature fortwo hours.

[0020] At the end of the reaction, the agitation was stopped and thesolids were allowed to settle. The supernatant was decanted, 200 ml oftoluene was added, the reaction media was heated to just below reflux,and was held for fifteen minutes at this temperature. The solids werethen allowed to settle and the supernatant was decanted. The toluenetreatment was then repeated.

[0021] Then, 30 ml of toluene and 20 ml of TiCl₄ were added, the mediawas heated to 115° C., and was held for one hour. After allowing thesolids to settle, the liquid was decanted, and the solids were treatedtwice with 200 ml of toluene as described above. After these treatments,the sequence of the TiCl₄-toluene reaction and two toluene treatmentswas repeated twice. After the last toluene decant, the solids werewashed five times with 100 ml each of hexane. The catalyst was thenisolated as a slurry.

[0022] Analysis of the solid catalyst component showed it to contain 21wt % Mg and 1.5 wt % Ti.

[0023] Catalyst Testing

[0024] A 4 liter autoclave equipped with an agitator was purged withnitrogen until oxygen and water have been reduced to acceptable levels.Then, under a N₂ purge, 50 ml of purified hexane was added to thereactor, followed by 7.0 mmole of TEAL and 0.48 mmole ofdicyclopentyldimethoxy-silane. The catalyst slurry prepared above,containing 4 to 6 mg of the solid catalyst, was added to 45 ml ofpurified hexane and then was added to the reactor. The reactor wasclosed and 2.5 l of purified propylene was added, followed by 3.6 l(STP) of H₂. The contents of the reactor were stirred and were heated to70° C. The reaction mixture was maintained at 70° C. for one or twohours. The reactor was then vented and cooled.

[0025] The resulting polymer was collected and dried. The polymer wasweighed and an activity, defined as kg polymer/g catalyst charged wascalculated. The polymer poured bulk density (PBD) and total xyleneinsolubles (TXI) were measured. The controlled particle sizedistribution and morphology of the starting support precursor wasmaintained in the polymer particles. The results of these tests wereshown in Table 1. In many cases, 2-3 tests were run on each catalyst andthe average results of these tests were reported.

EXAMPLE 2

[0026] A catalyst preparation was carried out using the proceduredescribed in Example 1, except that 25 ml of toluene and 25 ml of TiCl₄were used in the reaction steps. Analysis of the solid catalystcomponent showed it to contain 21 wt % Mg and 1.5 wt % Ti. Testing wascarried out as described in Example 1, and the results are shown inTable 1, below.

EXAMPLE 3

[0027] A catalyst preparation was carried out using the proceduredescribed in Example 1, except that 20 ml of toluene and 30 ml of TiCl₄were used in the reaction steps, and only 1×200 ml toluene treatment wasused after each TiCl₄/toluene reaction. Analysis of the solid catalystcomponent showed it to contain 19 wt % Mg and 1.8 wt % Ti. Testing wascarried out as described in Example 1, and the results are shown inTable 1, below.

EXAMPLE 4

[0028] A catalyst preparation was carried out using the proceduredescribed in Example 1, except that the reactor was a 250 ml roundbottom flask, 10 ml of toluene and 40 ml of TiCl₄ were used in thereaction steps, and 2×100 ml toluene treatments were used after eachTiCl₄/toluene reaction. Analysis of the solid catalyst component showedit to contain 19 wt % Mg and 1.6 wt % Ti. Testing was carried out asdescribed in Example 1, and the results are shown in Table 1, below.

EXAMPLE 5

[0029] A solid catalyst component was synthesized following theprocedure described in Example 1, except that the reactor was a 250 mlround bottom flask and 2×100 ml toluene treatments were used after eachTiCl₄/toluene reaction step. Analysis of the solid catalyst componentshowed it to contain 19 wt % Mg and 1.5 wt % Ti. Testing was carried outas described in Example 1, and the results are shown in Table 1, below.

EXAMPLE 6

[0030] The procedure described in Example 1 was used to prepare acatalyst, except that the reactor was a 250 ml round bottom flask andone 100 ml toluene treatment was used after each TiCl₄/toluene reactionstep. Analysis of the solid catalyst component showed it to contain 17wt % Mg and 3.0 wt % Ti. Testing was carried out as described in Example1, and the results are shown in Table 1, below.

EXAMPLE 7

[0031] A catalyst preparation was carried out using the proceduredescribed in Example 3, except that the reactor was a 250 ml roundbottom flask and 2×100 ml toluene treatments were used after eachTiCl₄/toluene reaction step. Analysis of the solid catalyst componentshowed it to contain 20 wt % Mg and 1.7 wt % Ti. Testing was carried outas described in Example 1, and the results are shown in Table 1, below.

EXAMPLE 8

[0032] A solid catalyst component was synthesized following theprocedure described in Example 3, except that the reactor was a 250 mlround bottom flask and 1×100 ml toluene treatment was used after eachTiCl₄/toluene reaction step. Analysis of the solid catalyst componentshowed it to contain 17 wt % Mg and 2.9 wt % Ti. Testing was carried outas described in Example 1, and the results are shown in Table 1, below.

EXAMPLE 9

[0033] A catalyst preparation was carried out using the proceduredescribed in Example 1, except that 40 ml of toluene and 60 ml of TiCl₄were used in each reaction step. Analysis of the solid catalystcomponent showed it to contain 20 wt % Mg and 1.2 wt % Ti. Testing wascarried out as described in Example 1, and the results are shown inTable 1, below.

EXAMPLE 10

[0034] A catalyst preparation was carried out using the proceduredescribed in Example 1, except that 60 ml of toluene and 40 ml of TiCl₄were used in each reaction step. Analysis of the solid catalystcomponent showed it to contain 20 wt % Mg and 1.5 wt % Ti. Testing wascarried out as described in Example 1, and the results are shown inTable 1, below.

EXAMPLE 11

[0035] An aliquot of the catalyst slurry prepared in Example 9 was driedunder vacuum. The test procedure described in Example 1 was followedexcept that the dry catalyst is added to the 45 ml of hexane instead ofa slurry. The results are found in Table 1, below.

EXAMPLE 12

[0036] A catalyst preparation was carried out using the proceduredescribed in Example 3, except that the reactor was a 250 ml roundbottom flask, and three series of TiCl₄-toluene reactions and 1×100toluene treatments are used. Analysis of the solid catalyst componentshowed it to contain 15 wt % Mg and 3.8 wt % Ti. Testing was carried outas described in Example 1, and the results are shown in Table 1, below.

EXAMPLE 13

[0037] A catalyst preparation was carried out using the proceduredescribed in Example 1, except that the reactor was a 250 ml roundbottom flask, and three series of TiCl₄-toluene reactions and 1×100toluene treatments were used.

[0038] Analysis of the solid catalyst component showed it to contain 15wt % Mg and 3.8 wt % Ti. Testing was carried out as described in Example1, and the results are shown in Table 1, below.

EXAMPLE 14

[0039] In this Example, 5.0 g of a mixed phase ClMg(OEt) was chargedinto a 250 ml 4-neck round bottom flask as described in Example 1. Then,30 ml of toluene was added, the mixture was stirred to suspend thesolid, 20 ml of TiCl₄ was added to the stirred slurry, the slurry washeated to 90° C., and 1.95 g of di-isobutylphthalate was added. Themixture was heated to 115° C. and was held at this temperature for twohours.

[0040] Following the procedure in Example 1, the supernatant wasdecanted, and two treatments with 100 ml of toluene each were carriedout. The TiCl₄+toluene reaction/toluene treatment step were repeatedthree additional times. The solids were then washed four times with 100ml heptane each time. An additional 100 ml of heptane was added to theflask, the slurry was transferred to a vacuum filter apparatus, filteredand dried.

[0041] Analysis of the solid catalyst component showed it to contain 21wt % Mg and 1.3 wt % Ti. Testing was carried out as described in Example1, except that the dry catalyst was added to the 45 ml of hexane insteadof a slurry. The results are shown in Table 1, below.

EXAMPLE 15

[0042] A slurry of a solid catalyst component was prepared in then samemanner as Example 14 with the exception that the di-isobutylphthalatewas added at room temperature after the addition of the initial TiCl₄charge. Analysis of the solid catalyst component showed it to contain 20wt % Mg and 1.4 wt % Ti. Polymerization testing results, obtained underthe same conditions as shown in Example 1, are found in Table 1, below.

EXAMPLE 16

[0043] A portion of the catalyst slurry obtained in Example 15 wasfiltered and vacuum dried. Table 1 contains the polymerization testresults for this catalyst, carried out under the conditions of Example1, modified for the use of dry catalyst as in Example 11. The results ofthis Example are not illustrated in Table 1.

EXAMPLE 17

[0044] The catalyst prepared in Example 1 was tested for polymerizationperformance as in Example 1, except that the test is run at 80° C. forone hour. The averaged results of two tests were as follows: activity,132.6 kg/g catalyst; poured bulk density, 0.474 g/ml; total xyleneinsolubles, 99.37 wt %.

COMPARATIVE EXAMPLE 1

[0045] The procedure described in Example 12 was followed to produce asolid catalyst component except that 1.43 g of phthaloyl dichloride wassubstituted for diisobutylphthalate. The results of polymerizationtesting using the procedure in Example 1, modified for the use of drycatalyst as in Example 11, are presented in Table 1, below.

COMPARATIVE EXAMPLE 2

[0046] A catalyst preparation was carried out using the proceduredescribed in Example 1, except that 40 ml of toluene and 10 ml of TiCl₄were used in the reaction steps. Analysis of the solid catalystcomponent showed it to contain 22 wt % Mg and 0.69 wt % Ti. Testing wascarried out as described in Example 1, and the results are shown inTable 1, below. TABLE 1 Catalyst Performance Results yield # Tests timeof kg/g PBD TXI Example # averaged run, hr cat g/ml wt %  1 3 1 85.50.468 98.82  1 1 2 120.6 0.473 98.93  2 2 1 74.3 0.458 98.96  3 2 1 76.40.479 98.86  4 2 1 66.9 0.487 98.95  5 2 1 80.9 0.472 98.96  6 2 1 77.50.467 98.99  7 3 1 69.1 0.483 98.96  8 3 1 69.5 0.470 98.88  9 3 1 69.10.470 99.03  9 1 2 100.2 0.478 98.95 10 2 1 60.7 0.453 98.78 11 2 1 46.30.410 98.88 12 2 1 53.5 0.472 98.49 13 2 1 65.0 0.457 99.00 14 3 1 48.60.428 99.04 15 1 1 87.9 0.424 98.80 16 2 1 66.0 0.359 98.67 Comp. 1 1 120.7 0.460 99.33 Comp. 2 2 1 35.9 0.407 99.37

EXAMPLE 18

[0047] In this Example, 5.0 g of a pure phase ClMg(OEt), as described inU.S. Pat. No. 5,262,573, was slurried with 30 ml of toluene and 20 ml ofTiCl₄. The slurry was heated to 90° C. and 1.94 g of diisobutylphthalatewas added. The remainder of the process was then carried out asdescribed in Example 1, using 100 ml of toluene for the treatment stepsand 30 ml of toluene and 20 ml of TiCl₄ for the reaction steps. Theproduct was washed with heptane and isolated by vacuum drying.

[0048] Testing was carried out as described in Example 1, and theresults are shown in the following Table: # Tests time of yield PBD TXIaveraged run, hr kg/g cat g/ml wt % 3 1 68.5 0.386 98.62

[0049] The foregoing Examples illustrate the following features andperformance characteristics of the catalyst. Examples 1-8 describe modesfor preparing the catalyst along with the effects of varying theTiCl₄/toluene ratio and number and volume of toluene treatments. Example1 versus Example 9, and Example 3 and 7 versus Example 10 show thebenefit of reducing the volume of the TiCl₄/toluene reaction mixturefrom 10 ml/g support precursor (Examples 9 and 10) to 5 ml/g supportprecursor (Examples 1, 3, and 7).

[0050] Example 9 versus Example 11 illustrates the improvement incatalyst performance when the catalyst is not dried and is isolated as aslurry versus isolation as a dry powder. Example 3 versus 12 and Example6 versus 13 exhibit the difference found for carrying out four versusthree treatment cycles. Example 9 versus Example 15 compares the effectsof the temperature of addition of the diisobutylphthalate (DIBP)internal donor, 70° C. versus room temperature, for catalysts isolatedas slurries (room temperature, higher activity).

[0051] Examples 14, 11, and 16 show the effect of the temperature ofaddition of the DIBP internal donor, 90° C. versus 70° C. versus roomtemperature, for catalysts isolated as dry powders (room temperature,higher activity).

[0052] Example 17 shows the increase in activity achieved when thepolymerization test is run at 80° C. instead of 70° C.

[0053] Example 18, which is best compared to Example 11 that used amixed phase ClMg(OEt) support precursor, shows the present inventionusing, as a starting reagent, a pure phase ClMg(OEt) material. Theactivity of the catalyst was almost 50% greater than that for the mixedphase support material.

[0054] Example 14 versus Comparative Example 1 shows the use of aphthalate ester, DIBP in this case, gives a superior catalyst to the useof the corresponding acid chloride, phthaloyl dichloride, when ClMg(OEt)is the support precursor (dry catalyst).

[0055] Comparative Example 2 versus Examples 1-4, shows that reducingthe volume % of TiCl₄ in the TiCl₄/toluene reaction mixture from 40% to20% causes a large loss in activity, not evident from the trend found inthe 80%-40% range.

[0056] The foregoing Examples, since they are being provided to merelyillustrate certain embodiments of the present invention, should not beconstrued in a limiting fashion. The scope of protection sought is setforth in the claims that follow.

We claim:
 1. A process for forming a propylene polymerization catalystwhich comprises: forming a combination of titanium tetrachloride, amagnesium-containing compound that can be converted to magnesiumdihalide and an internal electron donor in an aromatic hydrocarbonsolvent, with the proviso that, the magnesium-containing compound cannotbe a magnesium dialkoxide when the internal donor is a halo phthaloylderivative, and bringing that combination to elevated temperature toform an intermediate product; washing the intermediate product with anaromatic hydrocarbon solvent at elevated temperature to produce a washedproduct and a supernatant followed by decantation of the supernatanttherefrom; treating the washed product with titanium tetrachloride in anaromatic hydrocarbon solvent to form a treated product and a supernatantfollowed by heating of the treated product and supernatant, decantationof the supernatant therefrom, and washing of the treated product with anaromatic hydrocarbon solvent at elevated temperature; to produce awashed product and a supernatant followed by decantation of thesupernatant therefrom; treating the washed product with titaniumtetrachloride in an aromatic hydrocarbon solvent, at least one moretime, to form a treated product and a supernatant followed by heating ofthe treated product and supernatant, decantation of the supernatanttherefrom; and addition of an aliphatic hydrocarbon solvent to thetreated product with decantation of the solvent therefrom to form awashed product which can be used as a propylene polymerization catalyst.2. A process as claimed in Claim 1 wherein, after the formation of thewashed product resulting from addition of the aliphatic hydrocarbonsolvent, and addition of mineral oil is added to the washed productforming a slurry containing the propylene polymerization catalyst.
 3. Aprocess as claimed in Claim 1 wherein the aromatic hydrocarbon solventis an alkylbenzene solvent.
 4. A process as claimed in Claim 1 whereinthe magnesium-containing compound that can be converted to magnesiumdihalide is a magnesium chloroalkoxide that contains up to about twelvecarbon atoms in its alkyl moiety.
 5. A process as claimed in Claim 1wherein the internal electron donor is a phthalate ester that containsup to about twelve carbon atoms in its alkyl groups.
 6. A process asclaimed in Claim 1 wherein the aromatic hydrocarbon solvent is toluene,the magnesium chloroalkoxide is magnesium chloroethoxide, and thephthalate ester contains up to about twelve carbon atoms in its alkylgroups.
 7. A process as claimed in Claim 2 wherein the aliphatic solventis hexane.
 8. A process as claimed in Claim 4 wherein the magnesiumchloroalkoxide contains up to about twelve carbon atoms in its alkylmoiety.
 9. A process as claimed in Claim 5 wherein the phthalate estercontains up to about twelve carbon atoms in its alkyl groups.
 10. Aprocess as claimed in Claim 1 wherein the aromatic hydrocarbon solventis toluene, the magnesium-containing compound that can be converted tomagnesium dihalide is a magnesium chloroalkoxide, and the internalelectron donor is a phthalate ester that contains up to about twelvecarbon atoms in its alkyl groups.
 11. A catalyst for the polymerizationof propylene which comprises a titanium compound having at least onetitanium-halogen bond which is supported on an activated, amorphousmagnesium dihalide support that is essentially free of alkoxyfunctionality, said catalyst having the following physical parameters:weight percent titanium—less than 2%; weight percent phthalateester—from about 10% to about 25%; phthalate ester to titanium molarratio—from about 0.9 to about 2; weight percent magnesium—from about 14%to about 23%; magnesium to titanium molar ratio—from about 7 to about30; surface area—from about 250 m²/gm to about 500 m²/gm; porevolume—from about 0.2 cc/gm to about 0.5 cc/gm; and average porediameter—no more than about 50 Angstroms.
 12. A catalyst for thepolymerization of propylene which comprises a titanium compound havingat least one titanium-halogen bond which is supported on an activated,amorphous magnesium dihalide support that is essentially free of alkoxyfunctionality, said catalyst having the following physical parameters:weight percent titanium—from about 1% to less than 2.0%; weight percentphthalate ester—from about 10% to about 20%; phthalate ester to titaniummolar ratio—from about 1 to about 1.9; weight percent magnesium—fromabout 18% to about 21%; magnesium to titanium molar ratio—from about 14to about 29; surface area—from about 300 m²/gm to about 500 m²/gm; porevolume—from about 0.2 cc/gm to about 0.4 cc/gm; and average porediameter—no more than about 35 Angstroms.
 13. A catalyst for thepolymerization of propylene which comprises a titanium compound havingat least one titanium-halogen bond which is supported on an activated,amorphous magnesium dihalide support that is essentially free of alkoxyfunctionality, the titanium metal content in the catalyst being lessthan 2 wt %, based on the weight of the support, and a phthalate esterdonor, the surface area of the catalyst ranging from about 250 m²/gm toabout 500 m²/gm.
 14. A catalyst as claimed in Claim 13 wherein themagnesium dihalide support is derived from a magnesium chloroalkoxidethat contains up to about twelve carbon atoms in its alkyl moiety.
 15. Acatalyst as claimed in Claim 13 wherein the phthalate ester donorcontains up to about twelve carbon atoms in its alkyl groups. 16.Polypropylene comprising from no more than about 0.20 ppm titanium thatis formed by polymerizing propylene in the presence of the catalyst ofany of Claims 11-15.
 17. Polypropylene comprising from no more thanabout 0.15 ppm titanium that is formed by polymerizing propylene in thepresence of the catalyst of any of Claims 11-15.
 18. Polypropylenecomprising from no more than about 0.10 ppm titanium that is formed bypolymerizing propylene in the presence of the catalyst of any of Claims11-15.